97/98 Merc. 115 spark plug problem

[robertab99]

Our 1997-98 115 Merc. #OG465502 fouls the #1 cylinder after only 3 to 4 hours of running. The plug has a shiny black look and when put on a plug tester the spark jumps to the interior of the plug and not across the gap. The constant cleaning or replacement of this is become a real pain. This condition has been happening since new. We had it in to a local "Pro" and the next time out the same problem. The original plugs gave a lot of buzz to the radio and electronics so the recommended resistor plug was substituted. None of the other plugs show this condition at all, ever. All trolling is done by a Honda 15hp 4 stroke.<br /><br />Thanks!

 

[andy6374]

Re: 97/98 Merc. 115 spark plug problem

This sounds like the arcing. Do a search of it on this forum.

 

[Laddies]

Re: 97/98 Merc. 115 spark plug problem

Try to change the CDM from that cyl to another to see if the problem goes with it or stays on the same cyl

 

[robertab99]

Re: 97/98 Merc. 115 spark plug problem

Coil and wire were replaced and the condition continues!

 

[Laddies]

Re: 97/98 Merc. 115 spark plug problem

If your engine has coils and a switch box and not CDM ign. then you could have a bad switch box or there is always a chance of the top carb flooding

 

[robertab99]

Re: 97/98 Merc. 115 spark plug problem

It was a CDM that was replaced for sure and not a coil...... does that leave carb flooding as the last problem?<br /><br />Thanks!

 

[Laddies]

Re: 97/98 Merc. 115 spark plug problem

I woukld think thats pretty much the problem then, there is a freakly thing with CDM ign. though somethings a bad CDM on one cyl. will cause another cyl to have problems. Don't ask me why I don't have a clue, you should ck the idle mix adjustment on number 1 first and if you redo the carb be sure the float is the right height, there is a voltage adapter available to ck the CDM units it and the DVA would be cost prohibitive for anyone other than a professional serviceman to own